1. Field of the Invention
The present invention relates to treadmills. More specifically, the present invention relates to a treadmill with an endless belt that is suspended longitudinally and laterally, so that it can deflect downwards to absorb the impacts of a person walking or running on it.
2. Prior Art
Conventional treadmills provide a moving surface in the form of an endless belt traveling over a low friction surface between two rollers, so that a person can walk or run in a confined space. The low friction surface of the conventional treadmill is supported by a rigid unyielding frame. Sustained exercise of a type whereby the feet strike rigid, unyielding surfaces is popularly known as "high impact." High impact exercises have been proven to cause stress fractures, and other disabling injuries for some participants and many people cannot engage in any high impact activities because they could aggravate pre-existing conditions and/or hinder the rehabilitation of injuries.
Treadmills have been devised with yielding support structures under the endless belt such as the Treadmill Exercising Device with Yieldable Belt Support of Hagen U.S. Pat. No. 3,689,066 and the Exercise Treadmill Shock-Absorbing Improvement of Hanford U.S. Pat. No. 4,350,336. However, superior shock absorption capabilities are demonstrated by Lee et al with the Treadmill with Trampoline-Like Surface U.S. Pat. No. 4,548,405. This treadmill suspends the endless belt longitudinally between two rollers and laterally by a moveable spring suspension system over an essentially open frame. This complex suspension system supports the endless belt laterally by a plurality of springs attached along its edges. These springs are allowed to move with the endless belt by brackets containing rollers with anti-friction bearings that follow continuous tubular rails attached rigidly to the frame of the treadmill.
In the use of the Treadmill with Trampoline-Like Surface, it has been found that for best performance, the spring-carrying rollers must be made of a hard, low friction plastic such as acetal with Teflon.RTM., and that the continuous rails be fabricated from a polished, seamless, corrosion resistant material such as high-grade stainless steel tubing. If inferior materials are used, the overall friction of the system becomes too great for a person to walk or run without the aid of a powerful electric motor. Additionally, a film of light oil must be maintained on these continuous railings to produce an acceptable level of mechanical efficiency.
The painstaking fabrication of these continuous railings, and the complexity of the spring-carrying roller brackets, results in a much higher cost of manufacture than conventional treadmills. Also, the continuous rails force the spring-carrying roller brackets to make 180 degree turns as they follow the endless belt at speeds up to 10 MPH. The rapid and constant nature of these directional changes gives the Treadmill with Trampoline-Like Surface a much higher operating noise level than any conventional treadmill, which is objectional in many health-care facilities.